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Abstract:

A fault diagnosis unit 61 identifies that a system is out of order and
stops driving of a heater 51 (step S8) when a preset first setting time
elapses after a start of driving of an electric-powered water pump 42 and
a heater 51 (step S3 and step S4), a value obtained by subtracting
temperature detected by a heater inlet temperature sensor 52 from
temperature detected by a heater outlet temperature sensor 53 is less
than or equal to a preset first threshold (step S5), and a value obtained
by subtracting temperature detected by a water temperature sensor 43
before a start of driving of the electric-powered water pump 42 and the
heater 51 from temperature detected by the water temperature sensor 43 is
less than or equal to a second threshold (step S6).

Claims:

1. A vehicle air-conditioning system including a heat exchanger to heat
ventilating air by heat-exchanging the ventilating air to an interior of
a vehicle and a heat medium, a heater to heat the heat medium, and a pump
to circulate the heat medium within a cycling loop to which the heat
exchanger and the heater are connected, the system comprising: a first
temperature detector for detecting temperature of the heat medium flowed
in the heater; a second temperature detector for detecting temperature of
the heat medium flowed out from the heater; a third temperature detector
installed in the cycling loop for detecting temperature of the heat
medium in the cycling loop; and a fault identifying unit for identifying
that the system is out of order when a preset first setting time elapses
after a start of driving of the heater and the pump, a value obtained by
subtracting temperature detected by the first temperature detector from
temperature detected by the second temperature detector is less than or
equal to a preset first threshold, and a value obtained by subtracting
temperature detected by the third temperature detector before the start
of the driving of the heater and the pump from temperature detected by
the third temperature detector is less than or equal to a preset second
threshold.

2. The vehicle air-conditioning system according to claim 1, wherein the
fault identifying unit identifies that the system is out of order, in a
case where a state satisfying conditions continues for a preset second
setting time, the conditions being that the preset first setting time
elapsed after the start of the driving of the heater and the pump, the
value obtained by subtracting temperature detected by the first
temperature detector from temperature detected by the second temperature
detector is less than or equal to the preset first threshold, and the
value obtained by subtracting temperature detected by the third
temperature detector before the start of the driving of the heater and
the pump from temperature detected by the third temperature detector is
less than or equal to the preset second threshold.

3. A vehicle air-conditioning system including a heat exchanger to heat
ventilating air by heat-exchanging the ventilating air to an interior of
a vehicle and a heat medium, a heater to heat the heat medium, and a pump
to circulate the heat medium within a cycling loop to which the heat
exchanger and the heater are connected, the system comprising: a first
temperature detector for detecting temperature of the heat medium flowed
in the heater; a second temperature detector for detecting temperature of
the heat medium flowed out from the heater; and a fault identifying unit
for identifying that the system is out of order when a preset first
setting time elapses after a start of driving of the heater and the pump,
a value obtained by subtracting temperature detected by the first
temperature detector from temperature detected by the second temperature
detector is less than or equal to a preset first threshold, and a value
obtained by subtracting temperature detected by the first temperature
detector before the start of the driving of the heater and the pump from
temperature detected by the first temperature detector is less than or
equal to a preset second threshold.

4. The vehicle air-conditioning system according to claim 3, wherein the
fault identifying unit identifies that the system is out of order, in a
case where a state satisfying conditions continues for a preset second
setting time, the conditions being that the preset first setting time
elapsed after the start of the driving of the heater and the pump, the
value obtained by subtracting temperature detected by the first
temperature detector from temperature detected by the second temperature
detector is less than or equal to the preset first threshold, and the
value obtained by subtracting temperature detected by the first
temperature detector before the start of the driving of the heater and
the pump from temperature detected by the first temperature detector is
less than or equal to the preset second threshold.

5. A vehicle air-conditioning system including a heat exchanger to heat
ventilating air by heat exchanging the ventilating air to an interior of
a vehicle and a heat medium, a heater to heat the heat medium, and a pump
to circulate the heat medium within a cycling loop to which the heat
exchanger and the heater are connected, the system comprising: a first
temperature detector for detecting temperature of the heat medium flowed
in the heater; a second temperature detector for detecting temperature of
the heat medium flowed out from the heater; and a fault identifying unit
for identifying that the system is out of order when a preset first
setting time elapses after a start of driving of the heater and the pump,
a value obtained by subtracting temperature detected by the first
temperature detector from temperature detected by the second temperature
detector is less than or equal to a preset first threshold, and a value
obtained by subtracting temperature detected by the second temperature
detector before the start of the driving of the heater and the pump from
temperature detected by the second temperature detector is less than or
equal to a preset second threshold.

6. The vehicle air-conditioning system according to claim 5, wherein the
fault identifying unit identifies that the system is out of order, in a
case where a state satisfying conditions continues for a preset second
setting time, the conditions being that the preset first setting time
elapsed after the start of the driving of the heater and the pump, the
value obtained by subtracting temperature detected by the first
temperature detector from temperature detected by the second temperature
detector is less than or equal to the preset first threshold, and the
value obtained by subtracting temperature detected by the second
temperature detector before the start of the driving of the heater and
the pump from temperature detected by the second temperature detector is
less than or equal to the preset second threshold.

Description:

FIELD OF THE INVENTION

[0001] The present invention relates to an air-conditioning system for a
vehicle suitable for an electric vehicle and a hybrid vehicle, etc.

RELATED ART

[0002] In some electric vehicles and hybrid vehicles, there is one which
is equipped with a heater such as a Positive Temperature Coefficient
(PTC) heater, etc. for heating cooling water, installed on a cooling
water cycling loop on which a heater core and an electric water pump are
arranged.

[0003] In Patent Document 1, there is disclosed identifying a system
(e.g., an electric-powered water pump) failure, under such an
arrangement, based on a temperature difference between temperature of a
heater core and temperature detected by a water temperature sensor for
detecting temperature of cooling water in the cooling water cycling loop.

PRIOR ART DOCUMENT

[0004] Patent Document 1: JP 2005-343412 A

SUMMARY OF THE INVENTION

Problem to be Solved

[0005] In the above identification scheme based on the temperature
difference between the temperature of the heater core and the temperature
detected by the water temperature sensor, however, there are
circumstances, in some cases, where misidentification might be committed,
depending on heat exchange rates by the heater core.

[0006] For example, the heat exchange rates of the heater core are more
susceptible to be changed due to air quantity to be hit against the
heater core, and temperature at a blower outlet, etc. At this time, in
the event that the heat exchange rates of the heater core are little
(i.e., heat loss of the heater core is little), the temperature of the
heater core and the temperature detected by the water temperature sensor
rise while maintaining same difference value between the temperature of
the hear core and the temperature detected by the water temperature
sensor, which avoids an increase in the temperature difference. Hence, it
is likely to commit misidentification that the electric water pump etc.
is out of order.

[0007] An objective of the present invention is to conduct identification
of a system error with high accuracy using temperature detected by a
sensor, even when heat exchange rates of the heart core vary.

Solution to the Problem

[0008] To solve the above-identified problems, according to one embodiment
of the present invention, the invention may provide a vehicle
air-conditioning system including a heat exchanger to heat ventilating
air by heat-exchanging the ventilating air to an interior of a vehicle
and a heat medium, a heater to heat the heat medium, and a pump to
circulate the heat medium within a cycling loop to which the heat
exchanger and the heater are connected, the system comprising: a first
temperature detector for detecting temperature of the heat medium flowed
in the heater; a second temperature detector for detecting temperature of
the heat medium flowed out from the heater; a third temperature detector
installed in the cycling loop for detecting temperature of the heat
medium in the cycling loop; and a fault identifying unit for identifying
that the system is out of order when a preset first setting time elapses
after a start of driving of the heater and the pump, a value obtained by
subtracting temperature detected by the first temperature detector from
temperature detected by the second temperature detector is less than or
equal to a preset first threshold, and a value obtained by subtracting
temperature detected by the third temperature detector before the start
of the driving of the heater and the pump from temperature detected by
the third temperature detector is less than or equal to a preset second
threshold.

[0009] Further, in one aspect of the present invention, the fault
identifying unit may identify that the system is out of order, in a case
where a state satisfying conditions continues for a preset second setting
time, the conditions being that the preset first setting time elapsed
after the start of the driving of the heater and the pump, the value
obtained by subtracting temperature detected by the first temperature
detector from temperature detected by the second temperature detector is
less than or equal to the preset first threshold, and the value obtained
by subtracting temperature detected by the third temperature detector
before the start of the driving of the heater and the pump from
temperature detected by the third temperature detector is less than or
equal to the preset second threshold.

[0010] According to one aspect of the present invention, the embodiment
may provide a vehicle air-conditioning system including a heat exchanger
to heat ventilating air by heat-exchanging the ventilating air to an
interior of a vehicle and a heat medium, a heater to heat the heat
medium, and a pump to circulate the heat medium within a cycling loop to
which the heat exchanger and the heater are connected, the system
comprising: a first temperature detector for detecting temperature of the
heat medium flowed in the heater; a second temperature detector for
detecting temperature of the heat medium flowed out from the heater; and
a fault identifying unit for identifying that the system is out of order
when a preset first setting time elapses after a start of driving of the
heater and the pump, a value obtained by subtracting temperature detected
by the first temperature detector from temperature detected by the second
temperature detector is less than or equal to a preset first threshold,
and a value obtained by subtracting temperature detected by the first
temperature detector before the start of the driving of the heater and
the pump from temperature detected by the first temperature detector is
less than or equal to a preset second threshold.

[0011] According to one aspect of the present invention, the fault
identifying unit may identify that the system is out of order, in a case
where a state satisfying conditions continues for a preset second setting
time, the conditions being that the preset first setting time elapsed
after the start of the driving of the heater and the pump, the value
obtained by subtracting temperature detected by the first temperature
detector from temperature detected by the second temperature detector is
less than or equal to the preset first threshold, and the value obtained
by subtracting temperature detected by the first temperature detector
before the start of the driving of the heater and the pump from
temperature detected by the first temperature detector is less than or
equal to the preset second threshold.

[0012] According to one aspect of the present invention, the invention may
provide a vehicle air-conditioning system including a heat exchanger to
heat ventilating air by heat exchanging the ventilating air to an
interior of a vehicle and a heat medium, a heater to heat the heat
medium, and a pump to circulate the heat medium within a cycling loop to
which the heat exchanger and the heater are connected, the system
comprising: a first temperature detector for detecting temperature of the
heat medium flowed in the heater; a second temperature detector for
detecting temperature of the heat medium flowed out from the heater; and
a fault identifying unit for identifying that the system is out of order
when a preset first setting time elapses after a start of driving of the
heater and the pump, a value obtained by subtracting temperature detected
by the first temperature detector from temperature detected by the second
temperature detector is less than or equal to a preset first threshold,
and a value obtained by subtracting temperature detected by the second
temperature detector before the start of the driving of the heater and
the pump from temperature detected by the second temperature detector is
less than or equal to a preset second threshold.

[0013] According to one aspect of the present invention, the fault
identifying unit may identify that the fault identifying unit identifies
that the system is out of order, in a case where a state satisfying
conditions continues for a preset second setting time, the conditions
being that the preset first setting time elapsed after the start of the
driving of the heater and the pump, the value obtained by subtracting
temperature detected by the first temperature detector from temperature
detected by the second temperature detector is less than or equal to the
preset first threshold, and the value obtained by subtracting temperature
detected by the second temperature detector before the start of the
driving of the heater and the pump from temperature detected by the
second temperature detector is less than or equal to the preset second
threshold.

Advantageous Effect of the Invention

[0014] According to the present invention, since less influence of heat
exchange rates of the heat exchanger is exerted on the temperature
difference of the temperature detected by the first temperature detector,
the second temperature detector, or the third temperature detector,
before and after the start of the driving of the heater and the pump, the
invention enables with high accuracy identification of the occurrence of
system failure by using the temperature difference.

[0015] Furthermore, according to the present invention, since the system
failure is identified based on a plurality of conditions, the invention
enables to prevent inadvertent misidentification of system failure to
achieve identification of the occurrence of system failure with high
accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a view showing an exemplary construction of the vehicle
air-conditioning system according to the present embodiment;

[0017] FIG. 2 is a flow chart showing one example of fault diagnosis
process carried out by the controller;

[0018]FIG. 3 is a flow chart showing one example a procedure of driving
control of the heater;

[0019]FIG. 4 is a flow chart showing one example of fault diagnosis
process carried out by the controller in a variant of the present
embodiment; and

[0020]FIG. 5 is a flow chart showing another example of fault diagnosis
process carried out by the controller in a variant of the present
embodiment.

DESCRIPTION OF EMBODIMENTS

[0021] A description will be made to an exemplary construction of a
vehicle air-conditioning system 10 installed in a vehicle 1.

[0022] Construction

[0023] FIG. 1 is a view showing an exemplary construction of the vehicle
air-conditioning system according to the present embodiment. Here, the
vehicle 1 is a hybrid car.

[0024] As shown in FIG. 1, the vehicle air-conditioning system 10 includes
an air-conditioning unit 20, a heat medium circulating unit 40, and a
controller (e.g., an air-conditioning Electronic Control Unit (ECU)) 60.

[0025] As shown in FIG. 1, the air-conditioning unit 20 has a flow path
formed for air-conditioning air. Depending on a contour of the flow path,
a switching door 21, a blower fan (fan for air-conditioning) 22, an
evaporator core 23, a heater core 24, an air mix door (A/M door) 25, and
mode switching doors 26, 27 are disposed. In the air-conditioning unit
20, an outside air inlet 31, an inside air inlet 32, and blower outlets
33, 34, and 35 are provided, in correspondence with the switching door 21
and the mode switching doors 26, 27.

[0026] The switching door 21 opens and closes the outside air inlet 31 and
the inside air inlet 32. The vehicle air-conditioning system 10 is
configured to be possible to select, as an air induction mode, an inside
air cycling mode to induct inside air, and an outside air induction mode
to induct outside air. The switching door 21 opens and closes depending
on a selected induction mode. Further, in the air-conditioning unit 20,
the blower fan 22 is disposed between the outside air inlet 31 and the
outside air outlet 32, and the evaporator core 23.

[0027] The blower fan 22 is rotary-driven by a blower fan motor 28.
Thereby, air standing in the inside or the outside of a vehicle is
inducted to the air-conditioning unit 20 and is then supplied to the
evaporator core 23. As an alternative, driving stages of the blower fan
22 may be multiple (multiple stages).

[0028] The evaporator 23 performs heat exchange between refrigerant, which
is changed into high temperature and high pressure to be liquefied by
compressing the refrigerant using a compressor (not shown) and a
condenser (not shown), and air passing through the evaporator core 23.
Thereby, the air passing through the evaporator core 23 is cooled or
dehumidified when passing through the evaporator core 23. Also, by
selectively activating the compressor, air simply passes through the
evaporator core 23 when the evaporator core 23 does not perform cooling
or dehumidification. In the air-conditioning unit 20, the heater core 24
and the air mix door 25 are disposed at the downstream side of the
evaporator core 23.

[0029] The heater core 24 heats air to be passed therethrough. The heater
core 24 heats the air passing through the heater core 24 by circulating
heat medium such as cooling water, etc., between the engine 2 and the
heater core 24 by the heat medium circulating unit 40. Further, by
selectively activating the heater core 24, air simply passes through the
heater core 24 when the heater core 24 does not perform heating. As for
an arrangement of the heat medium circulating unit 40, a detailed
description will be made later.

[0030] In the air-conditioning unit 20, it is configured that air passed
through the heater core 24 and air bypassed the heater core 24 are mixed
therein, and that air quantity passed through the hater core 24 is
controlled by a degree of opening of the air mix door 25. Thereby, the
vehicle air-conditioning system 10 produces ventilation (air-conditioning
air stream) having preset temperature. Then, in the air-conditioning unit
20, the produced ventilation is inducted to the blower outlets 33, 34,
and 35.

[0031] The blower outlets 33, 34, and 35 include e.g., a defroster blower
outlet opened toward front wind glass of a vehicle; a register blower
outlet opened toward a passenger within a vehicle; and a front seat
underfoot blower outlet opened toward a passenger's feet seated on a
front seat. The blower outlets 33, 34, and 35 are selectively opened and
closed by the mode switching doors 26, 27.

[0032] Moreover, the controllable driving unit such as the aforesaid
switching door 21, the blower fan 22, the air mix door 25, and the mode
switching doors 26, 27 are controlled by the controller 60.

[0033] In the heat medium circulating unit 40, an electric-powered water
pump 42, an electric heater equipment 50, and a water temperature sensor
43 are disposed in a cycling loop 41 for circulating the cooling water.
The engine 2 is in the cycling loop 41. The electric-powered water pump
42 circulates cooling water heated by the engine 2 in the cycling loop
41. At this moment, the cooling water which is supplied from the
electric-powered water pump 42 passes through the electric heater
equipment 50, then through the water temperature sensor 43, and is
finally supplied to the heater core 24.

[0034] Here, the electric-powered water pump 42 is controlled by the
controller 60. A value detected by the water temperature sensor 43
(temperature detected by the water temperature sensor) is input to the
controller 60. The controller 60 controls driving of the electric-powered
water pump 42 and the electric heater equipment 50 based on the detected
value.

[0035] The electric heater equipment 50 includes a heater (e.g. PTC
heater) 51 that is an auxiliary heater which heats the cooling water
passing therethrough by electric energy; a heater inlet temperature
sensor 52 which is disposed at an inlet of the heater 51, and detects
temperature of the cooling water flowing into the heater 51; and a heater
outlet temperature sensor 53 which is disposed at an outlet of the heater
51, and detects temperature of the cooling water flowing out from the
heater 51.

[0036] The electric heater equipment 50 is controlled by the controller
60. For this reason, the controller 60 takes in a value detected by the
heater inlet temperature sensor 52 (i.e., heater inlet sensor
temperature), and a value detected by the heater outlet temperature
sensor 53 (i.e., heater outlet sensor temperature), where the controller
60 controls driving of the heater 51 based on these detected values. That
is, the controller 60 controls e.g., the driving of the heater such that
the cooling water rises up to required temperature based on these
detected values.

[0037] It goes without saying that the arrangement of the heat medium
circulating unit 40 is for illustration purpose only, and so the
electric-powered water pump 42, the electric heater equipment 50, and the
water temperature sensor 43 are granted liberty to take an alternative
without being necessarily limited to the arrangement, as mentioned above.

[0038] In the vehicle air-conditioning system 10 having such arrangement
as above, fault diagnosis of the system is conducted and process is
carried out depending on the results of the fault diagnosis. To this end,
the controller 60 includes a fault diagnosis unit 61. The fault diagnosis
unit 61 may e.g., be implemented by a device, or by a program.

[0039] FIG. 2 is a flow chart showing one example of fault diagnosis
process carried out by the controller 60.

[0041] In subsequent step S2, the controller 60 (e.g., a driving control
unit) controls the driving of the heater 51.

[0042]FIG. 3 is a flow chart showing one example of procedure of driving
control of the heater 51.

[0043] As shown in FIG. 3, firstly, in step S31, the controller 60
determines whether a start condition of driving of the heater 51 is
satisfied. For example, the controller 60 determines that the start
condition of driving is satisfied when the water temperature sensor
temperature Tw is less than or equal to preset temperature. The
preset temperature here is temperature necessary to drive the heater 51,
e.g., is temperature to be experimentally, empirically, or theoretically
set.

[0044] The process of the controller 60 proceeds to step S32 if it is
determined that the start condition of driving of the heater 51 is
satisfied. Otherwise, the process of the controller 60 proceeds to step
S33 if it is determined that the driving condition of the heater 51 is
not satisfied.

[0045] In step S32, the controller 60 starts to drive the heater 51. Then
the process of the controller 60 proceeds to step S33.

[0046] In step S33, the controller 60 determines whether a stop condition
of driving of the heater 51 is satisfied. For example, the controller 60
determines that the stop condition of the driving is satisfied when the
water temperature sensor temperature Tw is more than or equal to the
preset temperature, or when a preset time of period elapses after the
start of the driving of the heater 51. The preset temperature here is
temperature unnecessary to drive the heater 51, e.g., is temperature to
be experimentally, empirically, or theoretically set.

[0047] The process of the controller 60 proceeds to step S34 if it is
determined that the stop condition of driving of the heater 51 is
satisfied. Otherwise, the controller 60 then terminates process shown in
FIG. 3 if it is determined that the stop condition of driving of the
heater 51 is not satisfied.

[0048] In step 34, the controller 60 stops the driving of the heater 51.
Thus, the controller 60 terminates the process shown in FIG. 3.

[0049] As is demonstrated, in step S2, the controller 60 performs driving
control of the heater 51.

[0050] In succeeding step S3, the fault diagnosis unit 61 determines
whether the electric-powered water pump 42 and the heater 51 are driven.
More specifically, the fault diagnosis unit 61 identifies whether a
driving control signal to drive the electric-powered water pump 42 and
the heater 61 is output. The process of the fault diagnosis unit 61
proceeds to step S4, if it is determined that the electric-powered water
pump 42 and the heater 51 are driven, i.e., the driving control signal is
output. Otherwise, the process of the fault diagnosis unit 61 proceeds to
step S9, if it is determined that the electric-powered water pump 42 and
the heater 51 are not driven, i.e., the driving control signal is not
output.

[0052] In step S4, the fault diagnosis unit 61 determines whether a preset
driving continuation determination time a elapses after a start of
driving of the heater 51. Here, the preset driving continuation
determination time α is, e.g., a time until the detected value
detected by the heater inlet sensor temperature 52 (i.e., heater inlet
sensor temperature Tin), the detected value detected by the heater
outlet sensor temperature 53 (i.e., heater outlet sensor temperature
Tout), and the detected value detected by the water temperature
sensor 43 (i.e., water sensor temperature Tw) indicate a steady
value after the start of the driving of the heater 51. The time is set
experimentally, empirically, or theoretically.

[0053] The process of the fault diagnosis unit 61 proceeds to step S5 if
it is determined that the driving continuation determination time a
elapses after the start of the driving of the heater 51. Otherwise, the
fault diagnosis unit 61 terminates process shown in FIG. 2 if it is
determined that the driving continuation determination time a does not
elapse after the start of the driving of the heater 51.

[0054] In step S5, the fault diagnosis unit 61 determines whether a
difference (Tout-Tin) between the heater outlet sensor
temperature Tout and the heater inlet sensor temperature Tin is
less than or equal to a preset first heating determination threshold
Tth1. Here, the preset first heating determination threshold
Tth1 is e.g., a value set experimentally, empirically, or
theoretically. For example, a candidate of the preset first heating
determination threshold Tth1 may include 0 or its approximate value,
but it need scarcely be said that it is not necessarily limited thereto.

[0055] If the fault diagnosis unit 61 determines that the difference
between the heater sensor outlet temperature Tout and the heater
inlet sensor temperature Tin is less than or equal to the first
heating determination threshold Tth1 (i.e.,
Tout-Tin≦Tth1) the process proceeds to step S6.
Otherwise, if the fault diagnosis unit 61 determines to be not so (i.e.,
Tout-Tin>Tth1), the fault diagnosis unit 61 terminates
process shown in FIG. 2.

[0056] In step S6, the fault diagnosis unit 61 determines whether the
difference (Tw-T0) between the water temperature sensor temperature
Tw and the water temperature holding temperature T0 set in step S9
is less than or equal to a preset second heating determination threshold
Tth2. Here, the difference is a difference between the water
temperature sensor temperature Tw before a start of driving of the
electric-powered water pump 42 and the heater 51, and the water
temperature sensor temperature Tw after a start of driving (to be
specific, after elapse of time a after a start of driving) of the
electric-powered water pump 42 and the heater 51. Moreover, the second
heating determination threshold Tth2 is, e.g., a value set
experimentally, empirically, or theoretically. For example, a candidate
of the second heating determination threshold Tth2 includes 0 or its
approximate value, but it need scarcely be said that the threshold is not
necessarily limited thereto.

[0057] If the fault diagnosis unit 61 determined that the difference
between the water temperature sensor temperature Tw and the water
temperature holding temperature T0 is less than or equal to the second
heating determination threshold Tth2 (i.e.,
Tw-T0≦Tth2), the process proceeds to step S7. Otherwise,
if the fault diagnosis unit 61 determines to be not so (i.e.,
Tw-T0>Tth2), the fault diagnosis unit 61 terminates process
shown in FIG. 2.

[0058] In step S7, the fault diagnosis unit 61 determines whether the
satisfied state continues and a preset satisfied state continuation
determination time β elapses, after all determination conditions
insteps S3 to S6 are satisfied (i.e., all determination results are
"Yes"). In other words, the fault diagnosis unit 61 determines whether a
state where all determination conditions in steps S3 to S6 continues
during the preset satisfied state continuation determination time β.
Here, the satisfied state continuation determination time β is,
e.g., a time set experimentally, empirically, or theoretically.

[0059] If the fault diagnosis unit 61 determines that all determination
conditions in steps S3 to S6 are satisfied, its satisfied state
continues, and the preset satisfied state continuation determination time
β elapses, the process proceeds to step S8. Otherwise, if the fault
diagnosis unit 61 determines not to be so, the fault diagnosis unit 61
terminates process shown in FIG. 2.

[0060] In step S8, the controller 60 (e.g., driving control unit) stops
the driving of the heater 51. That is to say, the controller 60 stops
outputting the driving control signal to the heater 51.

[0061] Operation, etc.,

[0062] An explanation will then be made to one example of the vehicle
air-conditioning system 10 implemented by process shown in FIG. 2 as
above.

[0063] The vehicle air-conditioning system 10 detects the heater inlet
sensor temperature Tin, the heater outlet sensor temperature
Tout, and the water temperature sensor temperature Tw, as well
as drives the heater 51 depending on a start condition of driving and/or
a stop condition of driving, etc (step S1 and step S2).

[0064] At this moment, the vehicle air-conditioning system 10 sets the
water temperature sensor temperature Tw to the water temperature holding
temperature T0 until the start of the driving of the electric-powered
water pump 42 and the heater 51 is started (step S3 and step S9).

[0065] Then, when the driving of the electric-powered water pump 42 and
the heater 51 is started (i.e., when the driving control signal is
output), the vehicle air-conditioning system 10 performs process
according to the driving continuation determination time α, the
satisfied state continuation determination time β, the heater inlet
sensor temperature Tin, the heater outlet sensor temperature
Tout, and the water temperature sensor temperature tw (step S3
to step S8).

[0066] Namely, the vehicle air-conditioning system 10 identified that the
system is out of order and terminates the driving of the heater 51 when
the driving continuation determination time α elapses after the
start of the driving of the heater 51, a difference between the heater
outlet sensor temperature Tout and the heart inlet sensor
temperature Tin is less than or equal to the first heating
determination threshold Tth1, a difference between the water
temperature sensor temperature Tw and the water temperature holding
temperature T0 is less than or equal to the second heating determination
threshold Tth2, and these all conditions are satisfied and the
satisfied state continuation determination time β elapses. At this
moment, the vehicle air-conditioning system 10 may stop the
electric-powered water pump 42, as needed.

[0067] The system failure here includes a situation where the
electric-powered water pump 42 and/or the heater 51 are not operational,
or a situation where cooling water is in short supply, etc.

[0070] Since less influence of heat exchange rates of the heater core 24
is exerted on a temperature difference between the water temperature
sensor temperature Tw before the start of the driving of the
electric-powered water pump 42 and the heater 51 and the water
temperature sensor temperature T after the start of the driving of the
electric-powered water pump 42 and the heater 51, the vehicle
air-conditioning system 10 is capable of identifying with high accuracy
the occurrence of system failure by using the temperature difference.

[0071] That is, depending on conditions, such as air quantity of the
blower fan 22, driving stages of the blower fan 22, a degree of opening
of the air mix door 25, exterior air temperature, and blower outlet
temperature, etc., the heat exchange rates of the heater core 24 are
small. Accordingly, there may be a case where the temperature difference
between the heater outlet sensor temperature Tout and the heater
inlet sensor temperature Tin is small. In this situation, if system
failure identification is made by mistake only by relying upon the
temperature difference, erroneous identification of system failure could
occur. Meanwhile, where heat exchange rates of the heater core 24 are
small, it follows that temperature of the heat medium rises after the
driving of the electric-powered water pump 42 and the heater 51 is
started, and the water temperature sensor temperature Tw will rise
as a consequence.

[0072] From these facts, it is conceivable that less influence of the heat
exchange rates of the heater core 24 is exerted on the temperature
difference between the water temperature sensor temperature Tw
before the start of the driving of the electric-powered water pump 42 and
the heater 51 and the water temperature sensor temperature Tw after
the driving of the electric-powered water pump 42 and the heater 51.
Thus, the vehicle air-conditioning system 10 of the present embodiment
may identify the occurrence of system failure with high accuracy by using
the temperature difference.

[0073] In addition, since the vehicle air-conditioning system 10
identifies the occurrence of system failure based on multiple conditions
(i.e., conditions in step S4 to step S7), the vehicle air-conditioning
system 10 prevents inadvertent misidentification of the system failure,
thereby enabling with high accuracy identification of the occurrence of
system failure.

MODIFICATION TO THE PRESENT EMBODIMENT

[0074] A modification of the present embodiment is as follows.

[0075] The present embodiment is not necessarily limited to a
configuration where process in step S5 is carried out based on the water
temperature sensor temperature Tw. Put differently, in the present
embodiment, the process in step S5 can also be performed based on the
heater inlet sensor temperature Tin or the heater outlet sensor
temperature Tout.

[0076]FIG. 4 is a flow chart showing an exemplary process in a case where
the process is performed based on the heater inlet sensor temperature
Tin.

[0078] Then, in step S52 to which the process proceeds if it is determined
in step S3 that the electric-powered water pump 42 and the heater 51 are
not driven, the fault diagnosis unit 61 sets the heater inlet sensor
temperature Tin to the water temperature holding temperature T0.

[0079] Thereby, in step S53 to which the process proceeds if it is
determined in step S5 that a difference between the heater outlet sensor
temperature Tout and the heater inlet sensor temperature Tin
(i.e., Tout-Tin) is less than or equal to the first heating
determination threshold Tth1, the fault diagnosis unit 61 determines
whether a difference between the heater inlet sensor temperature Tin
and the water temperature holding temperature T0 set in step S52 (i.e.,
Tin-T0) is less than or equal to a preset third heating
determination threshold Tth3. Here, the difference is a difference
between the heater inlet sensor temperature Tin before the start of
the driving of the electric-powered water pump 42 and the heater 51 and
the heater inlet sensor temperature Tin after the start of the
driving of the electric water pump 42 and the heater 51 (to be specific,
after elapse of time a after a start of driving). Further, the third
heating determination threshold Tth3 is a value set, e.g.,
experimentally, empirically, or theoretically. For example, a candidate
of the third heating determination threshold Tth3 includes 0 or its
approximate value, but it need scarcely be said that the threshold is not
necessarily limited thereto.

[0080] If the fault diagnosis unit 61 determines that a difference between
the heater inlet sensor temperature Tin and the water temperature
holding temperature T0 is less than or equal to the third heating
determination threshold Tth3 (i.e., Tin-T0≦Tth3)
the process proceeds to step S7. Otherwise, if the fault diagnosis unit
61 determined not to be so (Tin-T0>Tth3), the fault
diagnosis unit 61 terminates process shown in FIG. 4.

[0081] With the process as above, in the modification to the present
embodiment, as with the effects of the aforesaid embodiment, since less
influence of heat exchange rates of the heater core 24 is exerted on the
temperature difference between the heater inlet sensor temperature
Tin, before and after the start of the driving of the electric water
pump 42 and the heater 51, the modification enables with high accuracy
identification of the occurrence of system failure by using the
temperature difference.

[0082] In the modification of the present embodiment, because multiple
conditions are used to identify the occurrence of system failure, the
modification prevents inadvertent misidentification of the system
failure, thereby enabling with high accuracy identification of the
occurrence of system failure.

[0083] Moreover, in the modification of the present embodiment, different
from the aforementioned embodiment, as it does not need to be provided
with the water temperature sensor 43, the modification allows
identification of the occurrence of system failure while suppressing an
increase in the number of the temperature sensor, or identification of
the occurrence of system failure even in a vehicle not equipped with the
water temperature sensor 43.

[0084]FIG. 5 is a flow chart showing an exemplary process in a case where
the process is carried out based on the heater outlet sensor temperature
Tout.

[0085] In this case, as shown in FIG. 5, firstly in step S51, the fault
diagnosis unit 61 fetches the value detected by the heater inlet
temperature sensor 52 (i.e., heater inlet sensor temperature Tin),
and the value detected by the heater outlet temperature sensor 53 (i.e.,
heater outlet sensor temperature Tout). Then, in step S61 to which
the process proceeds if it is determined in step S3 that the
electric-powered water pump 42 and the heater 51 are not driven, the
fault diagnosis unit 61 sets the heater outlet sensor temperature
Tout to the water temperature holding temperature T0.

[0086] Thereby, in step S62 to which the process proceeds if it is
determined in step S5 that a difference between the heater outlet sensor
temperature Tout and the heater inlet sensor temperature Tin is
less than or equal to the first heating determination threshold
Tth1, the fault diagnosis unit 61 determines whether a difference
between the heater outlet sensor temperature Tout and the water
temperature holding temperature T0 set in step S61, (i.e., Tout-T0),
is less than or equal to the preset fourth heating determination
threshold Tth4. Here, the difference is a difference between the
heater outlet sensor temperature Tout before the start of the
driving of the electric-powered water pump 42 and the heater 51 and
heater outlet sensor temperature Tout after the start of the driving
of the electric-powered water pump 42 and the heater 51 (to be specific,
after elapse of time a after a start of driving). Also, the fourth
heating determination threshold Tth4 is a value set, e.g.,
experimentally, empirically, or theoretically. For example, a candidate
of the fourth heating determination threshold Tht4 includes 0 or its
approximate value, but it need scarcely be said that the threshold is not
necessarily limited thereto.

[0087] If the fault diagnosis unit 61 determines that a difference between
the heater outlet sensor temperature Tout and the water temperature
holding temperature T0 is less than or equal to the fourth heating
determination threshold Tth4 (i.e., Tout-T0≦Tth4),
the process proceeds to step S7. Otherwise, if the fault diagnosis unit
61 determines not to be so (i.e., Tout-T0>Tth4), the fault
diagnosis unit 61 terminates process shown in FIG. 5.

[0088] With the process as above, in the modification of the present
embodiment, as with the effects of the aforesaid embodiment, because less
influence of heat exchange rates of the heater core 24 is exerted on the
temperature difference between the heater outlet sensor temperature
Tout before the start of the driving of the electric-powered water
pump 42 and the heater 51 and the heater outlet sensor temperature
Tout after the start of the driving of the electric-powered water
pump 42 and the heater 51, the modification enables identification with
high accuracy the occurrence of system failure by using the temperature
difference.

[0089] In the modification of the present embodiment, multiple conditions
are used to identify the occurrence of system failure, thus, the
modification prevents inadvertent misidentification of the system
failure, thereby enabling with high accuracy identification of the
occurrence of system failure.

[0090] Further, in the modification of the present embodiment, different
from the aforesaid embodiment, because it does not need to be provided
with the water temperature sensor 43, the modification allows
identification of the occurrence of system failure while suppressing an
increase in the number of the temperature sensor.

[0091] In the modification of the present embodiment, regardless of the
determination results in step S7, the driving of the heater 51 may be
stopped. In other words, in the modification of the present embodiment,
as long as all determination conditions (step S3 to step S6, step S3 to
step S5 and step S53, or step S3 to step S5 and step S62) are satisfied
(even when (β=0), the driving of the heater 51 may be stopped.

[0092] Thereby, the vehicle air-conditioning system 10 early identifies
the occurrence of system failure, and is allowed to stop the driving of
the heater 51.

[0093] Further, in the modification of the present embodiment, an
additional condition identifying that the engine is stopped may be added
to the determination conditions of step S3 to S7 (or step S3 to step S6).
In other words, in the modification of the present embodiment, if it is
identified that the engine is stopped, the driving of the heater 51 may
be stopped.

[0094] Thereby, because the vehicle air-conditioning system 10 identifies
the occurrence of system failure, with less influence upon temperature
detected by a sensor, due to heating of the cooling water by the engine,
the embodiment allows with high accuracy identification of the occurrence
of system failure.

[0095] In the modification of the present embodiment, the first, the
second, the third, and the fourth heating determination thresholds
Tth1, Tth2, Tth3, and Tth4 may be set based on
factors affecting the heat exchange rates of the heater core 24. That is,
for example, in the modification of the present embodiment, the first,
the second, the third, and the fourth heating determination thresholds
Tth1, Tth2, Tth3, and Tth4 may be set based on air
quantity of the blower fan 22, driving stages of the blower fan 22, a
degree of opening of the air mix door 25, exterior air temperature, or
diffuser temperature, etc.

[0096] Thereby, in the modification of the present embodiment, since the
first, the second, the third, and the fourth heating determination
thresholds Tth1, Tth2, Tth3, and Tth4 may be set,
taking a change in the heart exchange rates into account, the
modification allows with high accuracy identification of the occurrence
of system failure, even if the heat exchange rates are changed.

[0097] Further, in the modification of the present embodiment, fluid other
than water may be employed as heat medium.

[0098] In the modification of the present embodiment, the vehicle may be
an electric vehicle not equipped with an engine.